Abstract
Circular RNAs comprise a new class of long noncoding RNAs characterized by their 5′ and 3′ ends covalently joined. Previous studies have demonstrated that some circular RNAs act as microRNA sponges, and are associated with cellular proliferation in cancer. We were the first to analyze the global expression of circular RNAs in samples of patients without gastric cancer, gastric cancer, and matched tumor-adjacent gastric tissue. Among the samples, we identified 736 previously annotated circular RNAs by RNA-Seq. The tumor-adjacent tissue presented the higher abundance of circular RNAs and could not be considered as a normal tissue, reinforcing the notion of field effect in gastric cancer. We identified five differentially expressed circular RNAs that may be potential biomarkers of this type of cancer. We also predicted candidate microRNAs targets of the highest expressed circular RNAs in gastric tissues and found five miRNAs. Overall, our results support the hypothesis of circular RNAs representing a novel factor in the dynamic epigenetic network of gene regulation, which involves the microRNAs, its mRNAs targets, and the circular RNAs-derived genes. Further studies are needed to elucidate the roles and the functional relevance of the circular RNAs in human diseases.
Highlights
Circular RNAs comprise a new class of long noncoding RNAs characterized by their 5′ and 3′ ends covalently joined
CiRNAs and EIciRNAs are enriched in the nucleus and are RNA polymerase II-associated, suggesting that they promote the transcription of their parent genes[2,5,8,12,13]
Circular RNAs are a novel class of regulatory noncoding RNAs with yet unknown impact on the cellular machinery
Summary
Circular RNAs comprise a new class of long noncoding RNAs characterized by their 5′ and 3′ ends covalently joined. About 90,000 different circular RNAs were described in human, which most are derived mainly from annotated exons (~85%) and a smaller fraction from untranslated regions (UTRs), introns and unannotated regions of the genome They are most commonly formed from two or three exons, comprising between a hundred and four thousand nucleotides in length[1,2,5,6,7]. Circular RNAs molecules are accessed and measured in body fluids and have distinct characteristics such as tissue-specificity and stability in both intra and extracellular environments This suggest their potential as clinical markers that may provide new insights into the prevention and treatment of several diseases[14]
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